moffatt & nichol
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moffat t & n ichol
Passing Vessel Analysis in Design and Engineering
Eric D. Smith, P.E.
Vice President, Moffatt & Nichol
Passing Vessel Analysis in Port Engineering and Design
• Passing Vessel Effects
• Data Sources
• Passing Vessel Analyses
• Planning and Siting Studies
• Design Loads and Operational Criteria
• Forensic Investigations
• Management Methods
PASSING VESSEL EFFECTS
Passing Vessel Issues in Ports
• Vessel berths adjacent to navigation channels
• Increasing size of vessels
• Passing vessels create long-period wave forms with so-called “draw down” and current
• Effects induce forces and yaw moments on moored ships.
• Dynamic mooring models are required for analysis of passing effects (NOT static)
Vessel Hydrodynamic Effect
Passing Vessel Forces
From NAVFAC TR-6056-OCN “Mooring Loads Due to Parallel Passing Ships
Passing Vessel Forces
• Primarily surge/sway forcing
• Acts to pull vessels from mooring
Defining Passing Vessel Problem and Risks
• More common in congested and busy ports• May occur with right combination of speed,
distance, mooring configuration, and tide
• Broken mooring lines• Excessive movement• Damaged mooring hardware/fenders• Damage vessel hulls, loading equipment• Environmental risk: fuel spills• PERSONNEL SAFETY
• Mooring line snapback• Broken mooring components
Passing Vessel Mooring Analysis
Dynamic Mooring Model
Environmental Forces:
Wind, Wave, Current
Passing Vessel Loads Terminal
Configuration
Vessel
Characteristics
Hydrodynamics
Loads to Structures and Vessel Motions
Example Passing Vessel Models
• Empirical/Theoretical• PASS-MOOR (US Navy)
• Three Dimensional Potential Flow• DELPASS (Pinkster Marine Hydrodynamics)
• ROPES (Pinkster Marine Hydrodynamics)
• Computational Fluid Dynamics (future?)
Sources of Passing Vessel Data
• Port Pilots
• Simulator Studies
• AIS Data
• fleet monitoring websites
• data aggregators
• USCG
PLANNING AND SITING STUDIES
Passing Vessel Analysis Examples
Planning and Siting Studies
• ‘Greenfield’ Terminals
• Berth Orientation
• Set Back from Traffic Areas
• Dredging Limits
• Effects on Existing Navigation
• Safety
• Cargo Handling Efficiency and Throughput
Craney Island Eastward Expansion
• Expansion of dredge disposal area
• Planned containment dikes within 500 ft (150 m) of channel
• Planned future container port
• Determine effect of passing vessels and establish berth offset
Norfolk
Passing Vessels
• DELPASS – foundation of ROPES
• Basic scenario: inbound loaded containership with
moored containership
• 3 passing distances
• Passing speeds of 6-12 knots
185-338m
Inbound 6-12 knots
Surge Loads at 12 knots Passing
Mooring Model and Criteria
Dynamic Time Domain Simulations – Super Post-Panamax Ship
1. Line Loads <= 50% of Minimum Breaking Load (MBL)
2. Fender Load <= Rated Reaction
3. Vessel Motion per PIANC 1995
• For 100% Efficiency
• Surge <= 1.0m Sway <= 0.6m
• For 50% Efficiency
• Surge <= 2.0m Sway <= 1.2m
Lines 1-6Lines 11-16
7-89-10
Offset from Channel vs. Passing Speed
0
2
4
6
8
10
12
14
100 200 300 400
Pa
ss
ing
Sp
ee
d L
imit
(k
no
ts)
Wharf Distance from Navigation Channel (m)
Line Tension
Surge
Sway
Final Recommended Alignment
OPERATIONAL LIMITS AND DESIGN LOADS
Passing Vessel Analysis Examples
Design Loads and Operational Criteria
• Terminals Exposed to Larger Ships
• Contribution to Structural Loading
• Mooring Loads
• Fender Loads
• Configuration of Bollards/Hooks
• Safe Passing Speeds and Distance
• Protective Structures
• Navigation Markers
Passing Vessel AIS Data: Lake Charles, LA
AIS Data:
– Speed
– Track
– Size
– Loading condition
Passing Vessels at Example Terminal
• Identical vessel passing in channel
• 5, 6, 8 knots
• Look at coincident winds
• Passing on center and inside quarter
• Full/ballast draft
Passing Vessel: Mooring Line Tension Response
Dynamic Mooring ResponseMooring LinesFender ForcesMotions
Passing Vessel Results
Example: Mooring Analysis Results
• Vessels deploy 12 PP/PE mooring lines
• Wind limit 46 knots (30-sec gust)
• Quadruple hooks on mooring dolphins
• Mooring dolphin service load 150 tons
• Passing vessel speeds 5 knots or less
POST INCIDENT ANALYSIS
Passing Vessel Analysis Examples
Post Incident Analysis
• Gather Recorded Information and Anecdotal Accounts
• AIS Data
• Evidence of Damage
• Set Up Passing and Mooring Models to Recreate Incident
• Sensitivity on Unknown Parameters
• Attempt to Model Incident Conditions
• Recommendations for Infrastructure or Operation Improvements
Post Incident AIS Data
MANAGING
Passing Vessel Effects
Managing Passing Effects
• Navigation Management (pilots)
• Reduce Passing Speed
• Increase Passing Distance
• Mooring Management (ports)
• Additional or Stronger Mooring Lines
• Line Tending
• Upgraded Mooring Hardware
• Technologies
• Vacuum Pad Systems
• Constant Tension Systems
moffat t & n ichol
Thank You
…Discussion
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